1. Field of the Invention
The present invention relates to a belt for holding thereon a row of self-drilling screws so as to successively carry them into a power-driven screw-fastening tool (viz., power driver), wherein this tools usually of a portable type does operate at a high speed to drive and fasten those screws one by one to a pair of articles overlying one another. More particularly, the invention relates to such a belt especially adapted to hold and carry those screws each having reaming-blades protruding radially and disposed intermediate its drill bit and its male screw thread.
2. Prior Art
Some screw-holding belts of this type are disclosed in the Japanese Patent Publication No. 2520358. Typical examples are shown in FIGS. 7a, 7b, 8a and 8b of the drawings accompanying this specification.
Those prior art screw-holding belts do each comprise a row of screw-holding cylinders 2 formed in and along a belt body 1. Those simple and round cylinders 2 are disposed at regular intervals on the belt body 1 that is a band made of a soft flexible plastics. Each cylinder is adapted to receive and hold one screw at a threaded shank 7 thereof, wherein the screw has a head and a drill tip 8. Four slits 3 extend radially and outwardly from each screw-holding cylinder 2, in a pattern of the letter X. The outer ends of the slits 3 shown in FIG. 7a continue to round holes 4, whereas the ends of slits in FIG. 8a gradually increase their width towards their outer extremities to thereby form pointed and elongate holes 5. Only the upper inlet-side half of each screw-holding cylinder 2 in FIG. 8a is of a frustoconical or funnel shape opened upwards (towards the screw's head), so that the elongate holes 5 are formed in the conical wall of said inlet-side upper half. Such round or elongate holes 4 or 5 assist each cylinder 2 to expand and be broken. Thus each self-drilling screw's head will be allowed to pass easily and smoothly through said cylinder when a driver bit of the power driven apparatus strikes the screw off the belt body 1. Both the lateral sides of the belt body have cutouts 6 disposed at the same pitch as the screw-holding cylinders 2 so that the belt is caused to advance intermittently.
Soft articles of a wooden plate, a ply wood plate or the like are sometimes fixed to harder articles, for example those which are formed of profiled steels. The self-drilling screws used in such a case usually comprise reaming blades 9. Due to these reaming blades protruding radially and outwardly from the proximal ends of the drill bits 8 in a manner shown in FIGS. 7b and 8b, such screws are sometimes called "self-drilling reaming screws" (and hereinafter will be referred to as such).
It is however noted that although it has been necessary even for the self-drilling screws having such reaming blades to be fed automatically and intermittently, it has not been possible to hold them on any belt of the described structure. This is because the inner diameter of each screw-holding cylinder 2 is slightly smaller than the core diameter of the shank 7, whereas the reaming blades 9 protrude outwards beyond the crests of screw threads. In other words, such blades have been likely to give more or less damages to the cylinders 2 when inserted therein. If the blades 9 would undesirably be forced in the slits 3, then the former would be jammed on the latter's inner ends 3a (facing an inlet-side opening of the cylinder). In such an event, a lower outlet-side portion of the cylinder 2 would be cut off, thus failing to hold the screws upright relative to the belt body 1. As a result it has been almost impossible to employ any screw-holding belt for feeding the self-drilling reaming screws to the power-driven screw-fastening tools.